As is known, the distribution elements of an internal combustion engine (or more simply the distribution) are located on the head of the motor and allow to open and close alternately the intake and exhaust ports of the combustion chamber.
The most widespread type of distribution is constituted by camshafts, rods and rockers, which actuate mushroom valves which are adapted to open and close alternately the intake and exhaust ports of the combustion chamber.
Another type of distribution is also known which is termed rotary and has a distribution element constituted by a cylindrical rotor, which is connected kinematically to the engine shaft, rotates synchronously therewith and alternately closes and opens the ports for connecting the cylinders to the intake and exhaust conveyance channels.
A distribution of this type is disclosed in Italian patent No. 1172733 filed on Feb. 3, 1983 by this same applicant.
In this distribution, the cylindrical rotor (also known as rotary cylindrical distributor) is tubular and is divided, by means of dividing partitions, into substantially cylindrical internal chambers, two for each cylinder, each provided with at least two ports.
The head of the engine is constituted by a box-like body, which is arranged above the cylinders of the engine; the cylindrical distributor is arranged inside said body.
The box-like body is provided with side walls, a lower closure plate and an upper closure plate.
The plates and the walls are rigidly coupled by means of study bolts which pass through them and on related fixing portions provided on the upper part of the engine block on which the cylinders are provided.
There are also mutually opposite upper and lower sealing elements, two for each cylinder, which slide on the cylindrical distributor.
In particular, such sealing elements are provided with a cradle which is shaped complementarily with respect to the cylindrical distributor and a protrusion which protrudes from the cradle and is inserted in a respective through seat which is formed on the corresponding upper or lower plate.
A through hole is provided through the protrusion and the cradle and connects, if referred to the upper sealing element, the respective internal chamber of the rotary cylindrical distributor to the intake or exhaust conveyance channel, and, if referred to the lower sealing element, the respective internal chamber of the rotary cylindrical distributor with the combustion chamber of the cylinder (the internal chambers are therefore ports connecting the combustion chamber and the intake/exhaust).
Such sealing elements are accommodated with play (on the order of a few tenths of a millimeter) in such a way that it is possible to compensate the thermal deformations of the rotary cylindrical distributor and avoid its seizure.
In particular, the lower sealing element, once combustion has occurred inside the combustion chamber, tends to compensate the play, since it is pushed by the pressure of the combustion so as to form a seal against the rotary cylindrical distributor.
Although this type of distribution is known and has now been appreciated for many years, it is not free from aspects which can be improved, in particular in relation to the number of components that are present and to the compactness of the structure.